The present invention relates to a film feed device mounted in a camera or the like using a film having two perforations per frame.
Recently, a film having two perforations at predetermined positions per frame and a film feed device for a camera or the like using this film have been proposed.
This film has two perforations formed for the photographing area of each frame at predetermined positions. Film feed control can therefore be performed to accurately align the exposure aperture of the camera with each exposure area of the film by counting two perforations using one photoreflector (to be referred to as a PR hereafter) or detecting two perforations using two PRs.
In addition, such a film allows accurate film feed control in a photographing operation using the camera, and also allows film feed control for accurate film alignment in a printing process after development in a laboratory. For this reason, this film is expected to prevent an inappropriate printing process in an automatic printing apparatus.
The stop position of even such a film sometimes slightly deviates from a correct position owing to variations in the power supply voltage of the motor or environmental changes such as changes in temperature and humidity in a film feed operation.
In addition, if the power to the device is turned off during a film feed operation, the stop position of the film greatly deviates from a correct position.
Even if a film feed operation is properly performed, the film may move due to vibrations from some cause.
If a film feed is performed to the next frame in such a state of positional deviation, perforations are erroneously counted by the above method of controlling a film feed operation by using one PR. As a result, the stop position of the film may deviate from a correct position by one perforation.
Once perforations are erroneously counted, the positional deviation remains with respect to the subsequent frames.
If the method of simultaneously detecting two perforations by using two PRs is used, the above problem of positional deviation with respect to each frame can be solved. However, two processing circuits for perforation detection signals are required, hindering the miniaturization of the camera, and resulting in an increase in cost.